The improvement in the impact strength of polyamides is generally obtained by incorporating in the form of a disperse phase an impact strength modifier which is elastomeric in nature and has reactive functional groups (acrylic acid, maleic anhydride, etc.) capable of reacting with functional groups of the polyamide matrix. This reactivity makes it possible to ensure a fine and homogeneous dispersion of the elastomer, and a good adhesion at the matrix nodule interface, but results in a considerable drop in fluidity. This large change in the viscosity is detrimental to the processing, especially in the case of thin or large-sized injection mouldings.